The present invention relates to an apparatus and method for improving the performance and efficiency of a rotational wind energy conversion system.
Such systems, best known to the public, e.g., as windmills, suffer from several disadvantages which contribute to the failure of the public to fully utilize them in energy conservation programs.
One inherent limitation involves the inability of the rotors to respond to the great number of variations in wind velocity (gusts) which are present at all times. In other words, the response time of the conventional windmills (when rotor and shaft are rigidly connected) is too slow to extract energy from the many wind gusts. In some instances, the control system requires that the rotor-shaft be rotating at constant or almost constant speed. Furthermore, as a result of this inability of the rotor to "follow" the wind gust velocity, the hardware constituting the windmill (rotor, shafts, supporting structures, etc.), is subjected to mechanical shock caused by the energy imparted to the rotor by the wind gusts. In some cases, these shocks can excite the resonant frequencies of the mechanical structure which can cause additional stresses thereon. Such phenomena can also be caused by the rotor blade crossing the supporting tower "wind shadow".
Another drawback is that such wind harnessing devices cannot begin to extract rotational energy from the wind until a minimum "cut-in" wind velocity is achieved, e.g., 8-10 mph.
As a result of these and other disadvantages, the amount of time which a wind energy conversion system is operational and the efficiency with which it operates during those times are such that the applicability of such systems has been relatively limited.